In order to access locked premises, such as home or work, keys or key cards, for example, are still required for unlocking locks. For safety reasons, it is also increasingly common that people lock the doors and gates to backyards, housing sites or commercial buildings. This can be problematic when, for example, persons should have access to locked premises to which they do not have physical keys. Such a situation may occur when, for example, a resident is away from home and somebody, e.g. a cleaning service worker or a plumber, should have access to the locked premises. Such situations have usually been solved e.g. using master keys, hiding keys or, in the case of an electronic lock, for example, using ad hoc key codes.
Handing over conventional keys or cards to outsiders does, however, involve an increased safety risk. Keys may easily be lost, which means that the locks would have to be changed. Furthermore, even if e.g. a serviceman had a key, the key could be used for only as long as a corresponding lock is in use. It is also difficult to deliver extra keys e.g. to persons who only visit locked premises once, such as chimney sweepers. The use of electronic key codes is also problematic. Key codes are difficult to remember, and such codes require separate procedures in order to be activated. Furthermore, situations occur daily wherein somebody who has been authorized to conduct a task has not informed anybody about his or her visit in advance, so it has thus not been even possible to deliver a key or a code to such a person in advance. Furthermore, taking safety aspects into account considerably complicates the cooperation between people. For example, handing over a key code on the telephone to somebody asking for access would of course be possible, but the provider of the code would then immediately have to have the codes changed so as to prevent the particular person from using the same code later and entering the locked premises or from forwarding the code. A situation wherein access to locked premises is directly remotely controllable through a remote-controllable locking system, for example, would also involve a safety problem; in such a case, the remotely-situated controller of the locking system could not be sure of the identity of the person who wishes to be let in, nor whether it would be safe to grant access to such a person.